As an air disc brake for a railroad vehicle, a lever-operated air disc brake as shown in FIG. 4 has been proposed in Japanese Patent Unexamined Publication Hei. 7-9956, or the like.
The air disc brake 1 is configured as follows. A pair of brake blocks 4, 4 are disposed in opposition to each other so as to put therebetween a disc-like rotor 3 rotating integrally with a wheel 2. The brake blocks 4, 4 are driven by a pair of lever members 6, 6 and a single air chamber 8. The tip ends of the lever members 6, 6 are connected to the brake blocks 4, 4 respectively, and the single air chamber 8 is disposed between the opposite base end portions of the pair of lever members 6, 6 so as to turn the level members 6, 6.
The air chamber 8 is provided fixedly to a truck frame 7 of a railroad vehicle. When air pressure is supplied to the air chamber 8, a pair of operation plates 8a connected to the lever members 6 respectively are displaced so as to project out in the directions of the arrows (a) to thereby turn the lever members 6 around rotation fulcrums 9 in the directions of the arrows (b) respectively so that the brake blocks 4 are pressed against the rotor 3.
The lever members 6 are urged by return springs 10 respectively in the directions that the brake blocks 4 are separated from the rotor 3.
In the aforementioned lever-operated air disc brake, however, there arose a problem that not only the number of parts increased but also the size, weight and cost increased because of provisions of the lever members 6 and a mechanism for rotatably supporting the lever members 6.
Further, since the lever-operated air disc brake was configured so that the swelling displacement of the air chamber 8 caused by the supply of air pressure was transmitted to the brake blocks 4 through the lever members 6, the responsibility of the brake blocks 4 was lowered correspondingly to the interposition of the lever members 6 even in the case where air pressure supply control was performed at a high speed. Therefore, there arose a problem that the high-speed air pressure control was hardly reflected in improvement of the responsibility of the brake blocks 4.
Further, in the case of a railroad vehicle, there was a possibility that an axle might be moved within a range of about .+-.7 mm in an axial direction, a vertical direction or another direction at the time of braking. In the case of the aforementioned lever-operated air disc brake, an impact load acted on the rotation fulcrums 9 or the lever members 6 because of the aforementioned movement of the axle at the time of braking. Accordingly, there was a problem that constituent parts were fatigued easily.
The present invention is designed upon the aforementioned circumstances, and an object of the present invention is to provide an air disc brake in which the number of parts can be reduced to thereby attain reduction in size and weight and reduction in cost and in which air pressure supply control can be performed at a high speed to thereby improve responsibility easily. Further, it is another object of the present invention to provide an air disc brake in which an impact load acting on constituent parts due to the movement of an axle at the time of braking can be relaxed to thereby reduce the fatigue of the constituent parts caused by the impact load. Thus, the air disc brake according to the present invention is particularly adapted for a railroad vehicle.